BE 14106

Six new polyene macrolactams, heronamides G-L (1-6), one new polyenoic acid derivative, niveamide B (10), together with four known compounds, BE-14106-6 (7), BE-14106 (8), GT32-B (9), and niveamide (11), were isolated from the fermentation broth of Streptomyces niveus. Their planar structures were elucidated by detailed analysis of spectroscopic data. The absolute configurations of compounds 1-6 were determined by calculated ECD spectra and analysis of the possible biosynthetic pathways. Compounds 1-6 and 8-11 did not exhibit any significant antimicrobial activities, cytotoxicities, or inhibitory effects on lipopolysaccharide-induced NO production in BV2 microglial cells.

Heronamides are a class of potent antifungal metabolites produced by marine-derived actinomycetes. The number of hydroxy groups and the stereochemistry of the two hydroxylated methine carbons are important for the activity of heronamide C, whereas the effect of the hydrocarbon chains is not known. In this study, the stereochemistry and the biological activity of BE-14106, another member of the heronamide class of antibiotics, isolated from an actinomycete Actinoalloteichus cyanogriseus IFM 11549 was investigated. Spectroscopic analysis coupled with photo- and O2-induced conversion revealed that BE-14106 and the heronamides had the same stereochemistry. BE-14106 showed potent growth inhibition against fission yeast cells with an MIC value of 0.50 μM (0.21 μg/mL), being 4 times less potent than heronamide C, which revealed the importance of the structure of the hydrocarbon tail for the activity.

Streptomyces niveus NCIMB 11891 is the producer of the gyrase inhibitor novobiocin, which belongs to the aminocoumarin class of antibiotics. The genome sequence of this strain was found to contain, besides the gene cluster for novobiocin, a putative gene cluster for the macrolactam antibiotic BE-14106 and further secondary metabolite gene clusters.